<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <!-- 
        用表格来表示格式化数据
        table>tr>td
        tr表示行
        td表示一个格子
     -->
     <table border="1" width='50%' align="center">
         <tr>
             <td>a1</td>
             <td>b1</td>
             <td>c1</td>
             <td>d1</td>
         </tr>
         <tr>
            <td>a2</td>
            <td>b2</td>
            <td>c2</td>
            <!-- 合并纵向单元格 -->
            <td rowspan="2">d2</td>
        </tr>
        <tr>
            <td>a3</td>
            <td>b3</td>
            <td>c3</td>
    
        </tr>
        <tr>
            <td>a4</td>
            <td>b4</td>
            <td colspan="2">c4</td>
          <!-- 合并横向单元格 -->
        </tr>
     </table>
</body>
</html>